Because underground carbon resources are almost unlimited and carbon is harmless, carbon is an excellent material in view of resources problems and environmental problems. As carbon materials, a variety of crystal structures are known such as diamond, diamond-like carbon, graphite, fullerene, and carbon nanotube, depending on types of bonds between atoms. Particularly, diamond-like carbon (amorphous carbon) having an amorphous structure attracts attention as functional materials which are superior in mechanical properties such as abrasion resistance and solid lubricating ability and have insulation properties, visible light/infrared light transmittance, low permittivity, oxygen barrier properties and so on in combination, and its applications are expected in various industrial fields.
In general, amorphous carbon is formed on a surface of a substrate by chemical vapor deposition (CVD) or physical vapor deposition (PVD). For example, by plasma CVD, which is one of CVD techniques, an amorphous carbon film is formed by activating a carbon-containing raw material gas into a plasma state and depositing a reaction product on a surface of a substrate.
In addition to the above techniques, Japanese Unexamined Patent Publication Nos. 2003-297,598 and 2004-152,523 disclose generating bubbles in a liquid hydrocarbon (dodecane: C12H26) and generating plasma in the bubbles, thereby activating dodecane and forming an amorphous carbon film on a surface of a substrate.